Our lab seeks to understand the development formation and refinement of neural circuits within the mammalian brain. Our current focus is on a defined central circuit within the mouse olfactory bulb (OB) that specifically links iso-functional regions within each bulb. Since olfactory sensory input is organized through a set of stereotyped maps in the medial and lateral bulb understanding the formation of this circuitry and the nature of intrabulbar communication becomes central to understanding olfactory function. Previously we showed that the OB circuitry maintains a high level of plasticity particularly with regard to intrabulbar projections (reviewed, Cummings and Belluscio, 2008). We showed that the intrabulbar map that is mediated by these projections reorganizes its connectivity throughout life in an activity dependent manner. We are now utilizing in vivo time-lapse imaging to determine the precise neuronal subtypes and signaling molecules that regulate intrabulbar plasticity. At a functional level we recently showed that the medial and lateral halves of the OB receive olfactory sensory input that is temporally shifted and is modulated by odorant concentration (Zhou and Belluscio, 2012). Currently, we are using multielectrode recordings coupled with Optogenetic techniques to determine the role of intrabulbar projections in modulating this medial lateral olfactory bulb timing for coding in the pyriform cortex. Through our collaborative efforts with the Ibanez Lab at the Karolinska Institute we have also explored the molecular basis of OB circuit formation. We showed that Glial Derived Neurotrophic Factor (GDNF) is involved in OB development in particular signaling through the GFRa1 receptor (Marks et al., 2012). We are now investigating the role of such factors in intrabulbar plasticity as well.